Spark plug



Jim- 2 1 A. ANDERSON 2,870,363

SPARK PLUG Filed Aug. 11. 1955 INVENTOR BY mea M W AT TYS United States Patent SPARK PLUG Albin Anderson, Rockford, Ill.

Application August 11, 1955, Serial No. 527,754

4 Claims. (Cl. 313-143) This invention relates to novel and useful improvements in spark plugs for use in internal combustion engines.

An important object of this invention is to provide an improved spark plug construction for preventing the formation of deposits on the insulator tip and on the electrodes.

A more particular object of this invention is to provide a spark plug having a member arranged to provide a controlled circulation of combustion gases within the plug along the insulator tip to clean deposits forming thereon and which member also shields the insulator tip to aid in preventing oil or the like from spraying directly onto the tip.

A further object of this invention is to provide aspark plug having a member surrounding the insulator tip which is adapted to become heated during use to aidin burning oil the combustion products which tend to deposit on the insulator.

These, together with various ancillary objects and advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in connection with the accompanying drawings wherein:

Figure 1 is a side elevational view of a spark plug constructed in accordance with the present invention and having parts broken away and shown in section to illustrate details of construction;

Fig. 2 is a bottom view of the spark plug; and

Fig 3 is a side elevational View of the bafiie member for use in the spark plug to control the flow of combustion gases along the insulator tip.

The spark plug in general comprises a tubular metal body having an externally threaded lower end por tion 11 adapted to be threadedly received in the cylinder head. An elongated insulator 12-extends through the tubular body and has an enlarged intermediate portion 13, an upwardly extending neck portion 14 and a downwardly tapered tip portion 15. The insulator 12 is mounted at the intermediate portion 13 thereof in the plug body 10 and the tip portion 15' extends in spaced relation to the plug body to define a chamber therebetween which is open at the lower end of the plug. In the form illustrated, the plug body 10 is formed with an upwardly facing inwardly extending shoulder 17 intermediate the ends thereof for supporting the intermediate portion 13 of the insulator and a washer 18 is interposed between the insulator and the shoulder to provide a seal thereat. A gland 21 surrounds the neck, portion 14 of the in'su lator and is threaded into the internally threaded upper portion 22 of the plug body toengage an upwardly facing shoulder 24 formed on the insulator. A pressure distributing ring 23 is interposed between the gland and the shoulder 24 to prevent fracturing of the insulator when the gland is tightened. A center electrode 25 extends ,through the insulator and terminates at its upper end in ,a connector 26 adapted for connection to the wires of the ignition system. lower end of the center electrode projects below the insulator tip and below the lower end of the body 10. A second electrode 28 is atfixed to the plug body 10 and extends into closely spaced adjacency to the lower end of the center electrode to define a spark gap therebctween. 1

in accordance with the present invention there is provided a bafile member indicated generally by the numeral.

31 for controlling the circulation of the combustion gases within the plug and along the insulator tip. The bafile comprises a tubular member formed of a non-corrosive metal such as Monel metal and which is mounted in the plug body to extend between the insulator tip 15 and the body 10 and in spaced relation thereto. A convenient construction for mounting the bathe in the body is shown in the drawings and comprises an outwardly extending flange 33 formed on one end of the baffle, which flange is adapted to seat in an annular recess 34 formed in the shoulder 17 to support the bafile' on the body. A washer i8 overlies the junction between the flange 33 and the body to seal the interface therebetween and also seal the insulator to the plug body. If desired, any other suitable construction may be employed for mounting the baflle in the plugbody. The baflle member tapers downwardly and inwardly alongside the tip of the insulator, and in spaced relation thereto to divide the chamber at the lower end of the plug into two concentric compartments or passages 39a and 39b. The bafile member terminates at the lower end of the plug body between the end of the insulator tip 15 and the spark gap formed between the electrodes 25 and 28. An inwardly extending fiange 35 is formed on the lower end of the battle and surrounds the center electrode 25 to define a restricted central opening 36 therebctween. In order to prevent arcing between the baffle and the center electrode, the inner edge of the flange 35 is spaced radially from the center electrode a distance slightly greater than the length of the arc gap between electrodes 25,and 28. The opening 36 between the lower end of the baffle and the center electrode 25 is constructed to have a relatively small area as compared to the cross-sectional area of the passage formed between the baffie and the plug body 10. Preferably, the lower end of theinsulator tip 15 is made larger than the opening 36 in the lower end of the bafile and overlies this opening in closely spaced relation to the flange 35 on the baffie to further increase the resistance to the flow of gases upwardly through the openings 36. A plurality of annularly spaced apertures 37, here shown four in numher, are formed in the end of the bailie remote from the opening 36 and, in accordance with the present invention, are dimensioned to have an area which is sufi'iciently large to permit relatively free passage of the combustion gases therethrough. Preferably, the total area of the apertures 37 is made greater than the area of the opening 36 around the center electrode;

The above-described construction has been found in use to prevent the formation of undesired deposits on the tip of the insulator and'also on the electrodes, even in prolonged service under adverse conditions such as when the internal combustion engine begins to pump oil. The improved operation of the plug has been attributed to the controlled circulation of the combustion products Patented Jan. 20, 1959 v 3 the insulator tip. The bafiie member and plug body are dimensioned so that the flow passage 39a therebetween has a relatively large cross sectional area from the lower end of the bafile member to the upper end thereof adjacent the apertures 37, which passage is made suflicicntly large to permit combustible gas mixture to flow freely therein from the engine combustion chamber during the compression stroke of the engine. The lower end of the bafile member is shaped to extend into closely spaced adjacency to the center electrode and is spaced therefrom a minimum distance, slightly greater than the spark gap between the electrodes 25 and 28 to prevent shorting oi the latter. In practice, the opening is very small as compared to the cross section of the passage 3% and provides relatively restricted communication between the chamber 3% and the engine combustion chamber.

The walls of the bafifle member are made suthciently thin to become heated during use to assist in burning off any deposits which form on the insulator tip. As is well known, the heating of a plug will vary with the conditions under which it is used and it is customary to vary the plug construction such as the length of the insulator tip and the size of the electrodes in accordance with the temperature range in which the plug is to operate. it is contemplated that the thickness of the walls of the bafiie member be correspondingly varied to maintain the temperature of the battle member within a pre selected range during operation. Excessive heating of the battle member and other parts of the plug tends to cause pre-ignition whereas if the temperature of the battle member is too low, the bafile will be ineffective to aid in burning the deposits off from the insulator tip. In practice, the wall thickness is varied from .015 to .035

inch dependent on whether the plug is to operate at a low temperature or at a high temperature.

The operation of the plug in use in an internal combustion engine is thought to be as follows. At the completion of the exhaust stroke and before the intake stroke of the engine, the passages 39a and 3% are fiiled with exhaust gases. As the combustible mixture is in troduced into the combustion chamber of the engine and compressed therein, some of the combustible mixture will flow upwardly into the relatively large passage 3911 be tween the bafiie and the plug body. However, because of the restricted nature of the opening 36 into the lower end of passage 3%, little combustible gas will flow into this passage. When the charge in the combustion chamber is ignited at the spark gap between electrodes 25 and 23, externally of the bafile member, the flame passes upwardly in the passage 39a and rapidly builds up the pressure in the passage 3%. However, since only a small amount, if any, of combustible mixture passes into passage 39b and because of the restricted character of the opening 36, the flame does not pass upwardly from the spark gap into passage 3%. The pressure in this passage is thus lower than the pressure in the passage 3% and the burning gases in the last mentioned passage, therefore, flash through the apertures 37 into the chamer 3%. in practice, small brownish spots are found on the insulator tip opposite each of the apertures 37, after the plug has been in use, which indicate that the flames do pass from the passage 39a through the apertures 37 and produce a burning of any accumulated deposits on the insulator. The high pressure gases item the chamber 3% pass downwardly along the insulator tip from the apertures 37 and provide a scouring action which aids in burning and removing any accumulated deposits thereon.

The taper of the bafll'e member is made to correspond to the taper or the insulator tip to provide a somewhat uniform spacing therebetween which, as shown in Fig.1, is preferably small as compared to the spacing between the baffie and the plug body. This confined passage assures a rapid flow of gases along the insulator tip. The lower end of the insulator tip is extended to a point at closely adjacent the flange 55 to aid in restricting the opening 36. This causes the gases issuing from the chamber 3% to flow in a high velocity stream past the electrodes to maintain the latter clean.

I claim:

1. A spark plug including a hollow metal body, an insulator mounted in said body and having a tip portion extending in spaced relation thereto and defining a chamber therebetwcen open at the lower end of said body, a center electrode extending through said insulator and projecting below the lower end of the tip portion, a second electrode on said body defining a spark gap with the center electrode, a tubular bafile member mounted in said body inwardly ot the lower end thereof and extending downwardly in said chamber in spaced relation to the insulator tip and to the plug body and terminating at its lower end at a point between the lower end of the insulator tip and the spark gap, the lower end of said tubular member extending into closely spaced adjacency to said center electrode defining a restricted opening therebetween sufiicient to prevent arcing between the center electrode and the bafile member, said bafile member aving a plurality of annularly spaced apertures therein spaced above the lower end of said insulator, said bafilc member extending in spaced relation to said body between the lower end thereof and said apertures and defining a flow passage therebetween which is large as compared to said restricted opening to permit the flow of combustible gas upwardly between the bathe and the plug body.

2. A spark plug including a hollow metal body, an insulator mounted in said body and having a tip portion extending in spaced relation thereto and defining a cham ber therebetween open at the lower end of said body, a center electrode extending through said insulator and projecting below the lower end of the insulator tip, a second electrode on said body extending inwardly toward said center electrode and defining a spark gap therebetween, a tubular bafile member attached to said body and extending downwardly in said chamber in spaced relation to said insulator tip and to said body, said member having an inwardly extending flange on the lower end thereof extending inwardly around said center electrode between the end of the insulator tip and the spark gap and defining a restricted opening around the center electrode, the spacing of said flange from the center electrode being just sufiicient to prevent arcing therebetween, said member having a plurality of apertures formed therein adjacent the upper end of the insulator tip, the portion of said bafile member between said apertures and the lower end or" said bafile member extending in spaced relation to said body and defining a passage for combustion gases therebetween which is large as compared to said restricted opening whereby the gases in the combustion chamber tend to pass upwardly between said member and the body.

3. The combination of claim 2 wherein said insulator tip tapers downwardly and said tubular member tapers downwardly along the insulator tip in spaced relation thereto to form a relatively Wide opening between the lower end of said plug and said member.

4. A spark plug including a hollow metal body, an insulator mounted in said body and having a tip portion extending within said body in spaced relation thereto to a point above the lower end of said body, a center electrode extending through said insulator and projecting below the lower end of said body, a tubular bafile member mounted in said body adjacent the upper end of said tip portion of the insulator and extending downwardly in said body in spaced relation to the tip portion of the insulator and to said body, said member terminating at its lower and adjacent the lower end of the insulator tip and above the lower end of said center electrode and having an inwardly extending flange thereon at the lower end of said member extending inwardly around said center electrode and defining a restricted opening there'between, a second electrode attached to said base and ex tending inwardly below said flange into closely spaced adjacency to the center electrode to define a spark gap therewith, said tubular baffie member having a plurality of annularly spaced apertures located adjacent the upper end thereof to communicate the chamber between the baffle member and the body with the chamber between the baffle member and the insulator tip portion, said bathe member between said apertures and the lower end thereof extending in spaced relation to said body and defining a flow passage therebetween which is larger than said restricted opening whereby the combustion gases will flow more rapidly through said passage and said apertures than through said opening to provide circulation of gases up- References Cited in the file of this patent UNITED STATES PATENTS Re. 15,303 Blodgett et a1 Mar. 14, 1922 1,228,487 Sessions June 5, 1917 1,343,052 Heath June 8, 1920 1,361,580 Herz Dec. 7, 1920 1,371,431 Osterhout Mar. 15, 1921 2,172,844 Howel Sept. 12, 1939 

